The mission to colonize Mars, called Mars One, won't launch the first human crew until 2024. Although the journey is still long off — with several more chances to be cut from the roster — it's already weighing heavily on the Sullivan's relationship.

"The question is do we get divorced now or get divorced later," Ms. Sullivan told the Tribune. "If I stand in the way of his dreams and passions, then we get divorced now, so I have to be supportive."

Mr. Sullivan not only has his wife to think about. He also has four kids. The youngest is 6 months and the oldest is 13.

"Hopefully there isn't too much hatred of my being selfish in pursuing a dream that isn't theirs," Sullivan said about his family.

Sullivan is not alone in his aspirations. After a call went out last April, more than 200,000 applicants signed up for the flight to Mars, for which there is no return shuttle. In December, 1,058 candidates were told that they had made it to the second round.

The next selection phases will require candidates to pass several physical and emotional tests, according to Mars One's chief medical officer Nobert Kraft.